Metal Detecting at an Eighteenth Century Archaeological Site: Part II

Hello again! This is Amy Broussard, NCPTT Archaeology & Collections intern. With the guidance and supervision of Tad Britt, we are testing an eighteenth-century archaeological home site in northwest Louisiana, incorporating the use of a metal detector. My previous post provided an introduction to the project and detailed the legal and ethical implications of “treasure hunting,” so I’ll skip the lecture. This time I’ll describe the work we have completed thus far,giving readers a realistic look at archaeology in Louisiana.

Before entering the field, extensive research was conducted in order to understand the historic and ecological context of the area. The site was previously documented in the 1970s as part of a requisite cultural resource evaluation, resulting in several reports which we accessed via the Louisiana Division of Archaeology database. Additionally, we reviewed descriptions of nearby sites and collected historic plat maps and topographic quad sheets. We consulted with NSU professor, Dr. Hiram “Pete” Gregory, who worked at this site among others in the Red River and Cane River areas. I still plan to visit the Natchitoches parish clerk of court and see if I can ‘dig up’ any useful records or early survey maps that were not available online. Finally, in hopes of learning from example, I reviewed several recommended case studies that effectively combined metal detecting and archaeology (references at end of post).

The site location was covered with dense undergrowth vegetation until a few weeks before fieldwork began, when most of the young trees and saplings were removed. Trees that were too large to be cut by hand – mostly pine – remained standing. According to GPS data the resultant cleared area was 1658.94 square meters – a little under half an acre.

Using tape measures, we laid out a 25m x 25m grid called Metal Detecting Area 1 (MD Area 1), situated in the southwest corner of the cleared area. We placed a plastic stake every two meters along western (near road) and eastern (downhill) boundaries: 13 stakes on each side, 12 transects total (see sketch map).

Math isn’t my forte, but a little geometry is necessary to calculate the hypotenuse of a grid and the volume of excavated units.

So far we have conducted metal detecting in three transects: 1, 3, and 7. Before using the detector we raked the surface of each transect, removing pine needles and any debris that was obviously modern litter (aluminum cans, plastic shotgun cartridges, glass bottles, etc.). The metal detector operator swept the device back and forth, covering the 2-meter width of the transect from start to finish. Red PVC flags were placed at pin-pointed “targets” where the metal detector emitted a tone. After the detecting was complete, each red flag was excavated as a shovel test pit (STP). This initial phase of fieldwork resulted in a total of 118 STPs.

In this test pit, the soil stratigraphy is particularly well-defined, which is often not the case. The trowel points north.

We removed the soil by layers according to natural stratigraphy, down to a terminus of sterile clay. Each hole was approximately 30cm x 30cm diameter with an average depth of 18.8cm below surface. Soil was screened through a ¼” wire mesh, and artifacts were bagged and labeled according to provenience.

Some of the targets turned out to be modern metal just below the surface – a few brass shotgun heads, some tin or aluminum cans, and a few chainsaw blades, which we did not collect. The vast majority of artifacts recovered were oxidized iron square nails. There were a few diagnostic finds including a red-paste ceramic with a dark red and black glaze, two Civil War-era lead bullets, and a metal button still partially covered with a few visible fibers of worn fabric. The artifacts were cleaned, dried and re-bagged at the NCPTT lab, where they are being catalogued, photographed, analyzed and curated. Dealing with the artifacts is a very methodical process, and there are many ways for the archaeologist to categorize the material and interpret the qualitative and quantitative data… but that sounds like a good topic for my next post! Until we return to the field, I’ll be conducting more research, working with Photoshop, and drafting the report.

One of the many hand-wrought square nails we have collected. This spike is the largest we have found fully intact so far.

To be perfectly honest, we’re not sure what this is.. YET. Can you figure it out before I do? If you have a guess, comment on the facebook post!

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References

These are a few of the sources I turned to for an example of effective metal detective use at archaeological sites. Metal detecting is most commonly used at battlefield sites – like the most renowned case, at Little Bighorn. However, because our site was primarily documented as a home site associated with agriculture, and because our work is limited to the confines of a relatively small cleared area, I focused my reading on work conducted at similar locations.

Wettstaed, James R. 2003b Cutting it Back and Burning it Black: Archaeological Investigations of Charcoal Production in the Missouri Ozarks. IA, Journal of the Society for Industrial Archaeology 29(2):29-46.

Wettstaed, James R. 2012 The Utility of Metal Detectors in Delineating and Defining Archaeological Sites. Part of the Proceedings of the Advanced Metal Detecting for the Archaeologist Conference in Helen, Georgia. Edited by Terry G. Powis.